The invention relates to a method for removing material from a component. This machining is also called electro-chemical machining (ECM) or even precise electro-chemical machining (PECM).
With this method, the component from which material is supposed to be removed is connected as an anode. An electrode is guided to the component, and namely a gap is formed between the electrode and the component. Typically, the shape of the electrode is a counterpart of the shape that the component is supposed to achieve. The electrode is connected as a cathode, and an electrolyte must then be introduced between the cathode (electrode) and the anode (component), i.e., into the gap.
It is now necessary for the method to be carried out such that the removal takes place precisely at a predetermined surface area of the component and not in the surrounding areas. However, the latter can absolutely be etched by the electrolytes, particularly if the electrolyte is situated on the component on the other side of the actual effective surface, and if stray currents are flowing. Another problem is that the electrolyte gets used up during the process. As a result, the electrolyte must be replaced. If this does not occur uniformly, locally there can be depositions of the material removed from the work piece carried over in a hydroxide. At such locations, the conductivity of the electrolyte is diminished, which can lead to the electrode drifting on the component and thereby producing a short circuit.
There are numerous methods of the cited type, in which the electrolyte is guided via the electrode. In the present case, the electrolyte is not supposed to be conveyed via the electrode. Until now, there have been electrolyte systems for this with closed pressure chambers, in which the component to be machined is protected by guard electrodes outside the actual areas being machined (the so-called machining area). The disadvantage of this is that the electrolyte completely circulates around the component. The guard electrodes get used up. There is also the possibility of making an open system available, in which the electrolyte is directed via nozzles into the gap. The disadvantage of this method is that the flow in the gap is not uniform making it possible for flow grooves or dead water zones with hydroxide sludge accumulations to occur.
The object of the invention is making available a method for removing material from a component that eliminates the problems of the prior art.
Thus, a duct is formed, which has an inlet opening and an outlet opening, wherein the component forms a wall with a part of its surface and the electrode also forms a wall of the duct with at least one part of its surface. During removal, the electrolyte is continuously guided from the inlet opening to the outlet opening.
A closed system is produced by forming a duct. The electrolyte thereby reaches only the area from which material is supposed to be removed (which is being machined), and no etching occurs in the unprotected neighboring areas. Because electrolyte is continuously directed or guided through the duct, there is a reliable replacement of the used electrolyte, i.e., there is always enough fresh electrolyte in front of the electrode. As a result, one maintains a high feed rate during machining, because the process can proceed in a trouble-free manner. The electrolyte flow is particularly uniform and with a suitable formation of the duct it is also not turbulent so that there are no dead water zones and the hydroxide can be flushed out easily.
The uniformity of the electrolyte flow can be guaranteed especially reliably by the electrolyte being introduced into the inlet opening of the duct at a pressure of 2 to 50 bar, wherein a suitable nozzle is preferably used for this.
The formation of the duct can be accomplished in an especially simple manner by providing two (in particular non-conductive) guide elements that bridge the gap. The guide elements can be mounted on the component or even attached manually, however, it has proven to be especially readily convenient to accomplish if the guide elements are arranged or mounted on the electrode (i.e., are a part of the electrode unit). Then, when moving the electrode toward the component, the guide elements make contact with the surface of the component, while forming the gap, so that immediately with the formation of the gap, the duct is also formed in its final size.
There are also cases in which a duct is made available more or less automatically by the shape of the component on the electrode. This is particularly the case if the component supplied is a component that has a recess, and if an electrode configured as a formed electrode tool is used, which engages precisely in the component. Then just by forming the gap, the duct is formed.
In the case of this type of arrangement, the depth of the recess is supposed to be increased by the removal process, and not necessarily in terms of its lateral dimensions. As a result, it is expedient to partially coat the electrode with an insulating body such that an electrical connection of the electrode with the component is made possible via the electrolyte only in one section of the duct.
A preferred case in which the method can be used is producing engine components made of nickel-based or titanium-based alloys. In this case, the engine component is the component arising from the original component through machining. Such a typical engine component is a blade profile.
Preferred embodiments of the invention are described in the following making reference to the drawings.